1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Common capabilities, needed by capability.o.
3 */
4
5 #include <linux/capability.h>
6 #include <linux/audit.h>
7 #include <linux/init.h>
8 #include <linux/kernel.h>
9 #include <linux/lsm_hooks.h>
10 #include <linux/file.h>
11 #include <linux/mm.h>
12 #include <linux/mman.h>
13 #include <linux/pagemap.h>
14 #include <linux/swap.h>
15 #include <linux/skbuff.h>
16 #include <linux/netlink.h>
17 #include <linux/ptrace.h>
18 #include <linux/xattr.h>
19 #include <linux/hugetlb.h>
20 #include <linux/mount.h>
21 #include <linux/sched.h>
22 #include <linux/prctl.h>
23 #include <linux/securebits.h>
24 #include <linux/user_namespace.h>
25 #include <linux/binfmts.h>
26 #include <linux/personality.h>
27 #include <linux/mnt_idmapping.h>
28
29 /*
30 * If a non-root user executes a setuid-root binary in
31 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
32 * However if fE is also set, then the intent is for only
33 * the file capabilities to be applied, and the setuid-root
34 * bit is left on either to change the uid (plausible) or
35 * to get full privilege on a kernel without file capabilities
36 * support. So in that case we do not raise capabilities.
37 *
38 * Warn if that happens, once per boot.
39 */
warn_setuid_and_fcaps_mixed(const char * fname)40 static void warn_setuid_and_fcaps_mixed(const char *fname)
41 {
42 static int warned;
43 if (!warned) {
44 printk(KERN_INFO "warning: `%s' has both setuid-root and"
45 " effective capabilities. Therefore not raising all"
46 " capabilities.\n", fname);
47 warned = 1;
48 }
49 }
50
51 /**
52 * cap_capable - Determine whether a task has a particular effective capability
53 * @cred: The credentials to use
54 * @targ_ns: The user namespace in which we need the capability
55 * @cap: The capability to check for
56 * @opts: Bitmask of options defined in include/linux/security.h
57 *
58 * Determine whether the nominated task has the specified capability amongst
59 * its effective set, returning 0 if it does, -ve if it does not.
60 *
61 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
62 * and has_capability() functions. That is, it has the reverse semantics:
63 * cap_has_capability() returns 0 when a task has a capability, but the
64 * kernel's capable() and has_capability() returns 1 for this case.
65 */
cap_capable(const struct cred * cred,struct user_namespace * targ_ns,int cap,unsigned int opts)66 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
67 int cap, unsigned int opts)
68 {
69 struct user_namespace *ns = targ_ns;
70
71 /* See if cred has the capability in the target user namespace
72 * by examining the target user namespace and all of the target
73 * user namespace's parents.
74 */
75 for (;;) {
76 /* Do we have the necessary capabilities? */
77 if (ns == cred->user_ns)
78 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
79
80 /*
81 * If we're already at a lower level than we're looking for,
82 * we're done searching.
83 */
84 if (ns->level <= cred->user_ns->level)
85 return -EPERM;
86
87 /*
88 * The owner of the user namespace in the parent of the
89 * user namespace has all caps.
90 */
91 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
92 return 0;
93
94 /*
95 * If you have a capability in a parent user ns, then you have
96 * it over all children user namespaces as well.
97 */
98 ns = ns->parent;
99 }
100
101 /* We never get here */
102 }
103
104 /**
105 * cap_settime - Determine whether the current process may set the system clock
106 * @ts: The time to set
107 * @tz: The timezone to set
108 *
109 * Determine whether the current process may set the system clock and timezone
110 * information, returning 0 if permission granted, -ve if denied.
111 */
cap_settime(const struct timespec64 * ts,const struct timezone * tz)112 int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
113 {
114 if (!capable(CAP_SYS_TIME))
115 return -EPERM;
116 return 0;
117 }
118
119 /**
120 * cap_ptrace_access_check - Determine whether the current process may access
121 * another
122 * @child: The process to be accessed
123 * @mode: The mode of attachment.
124 *
125 * If we are in the same or an ancestor user_ns and have all the target
126 * task's capabilities, then ptrace access is allowed.
127 * If we have the ptrace capability to the target user_ns, then ptrace
128 * access is allowed.
129 * Else denied.
130 *
131 * Determine whether a process may access another, returning 0 if permission
132 * granted, -ve if denied.
133 */
cap_ptrace_access_check(struct task_struct * child,unsigned int mode)134 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
135 {
136 int ret = 0;
137 const struct cred *cred, *child_cred;
138 const kernel_cap_t *caller_caps;
139
140 rcu_read_lock();
141 cred = current_cred();
142 child_cred = __task_cred(child);
143 if (mode & PTRACE_MODE_FSCREDS)
144 caller_caps = &cred->cap_effective;
145 else
146 caller_caps = &cred->cap_permitted;
147 if (cred->user_ns == child_cred->user_ns &&
148 cap_issubset(child_cred->cap_permitted, *caller_caps))
149 goto out;
150 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
151 goto out;
152 ret = -EPERM;
153 out:
154 rcu_read_unlock();
155 return ret;
156 }
157
158 /**
159 * cap_ptrace_traceme - Determine whether another process may trace the current
160 * @parent: The task proposed to be the tracer
161 *
162 * If parent is in the same or an ancestor user_ns and has all current's
163 * capabilities, then ptrace access is allowed.
164 * If parent has the ptrace capability to current's user_ns, then ptrace
165 * access is allowed.
166 * Else denied.
167 *
168 * Determine whether the nominated task is permitted to trace the current
169 * process, returning 0 if permission is granted, -ve if denied.
170 */
cap_ptrace_traceme(struct task_struct * parent)171 int cap_ptrace_traceme(struct task_struct *parent)
172 {
173 int ret = 0;
174 const struct cred *cred, *child_cred;
175
176 rcu_read_lock();
177 cred = __task_cred(parent);
178 child_cred = current_cred();
179 if (cred->user_ns == child_cred->user_ns &&
180 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
181 goto out;
182 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
183 goto out;
184 ret = -EPERM;
185 out:
186 rcu_read_unlock();
187 return ret;
188 }
189
190 /**
191 * cap_capget - Retrieve a task's capability sets
192 * @target: The task from which to retrieve the capability sets
193 * @effective: The place to record the effective set
194 * @inheritable: The place to record the inheritable set
195 * @permitted: The place to record the permitted set
196 *
197 * This function retrieves the capabilities of the nominated task and returns
198 * them to the caller.
199 */
cap_capget(const struct task_struct * target,kernel_cap_t * effective,kernel_cap_t * inheritable,kernel_cap_t * permitted)200 int cap_capget(const struct task_struct *target, kernel_cap_t *effective,
201 kernel_cap_t *inheritable, kernel_cap_t *permitted)
202 {
203 const struct cred *cred;
204
205 /* Derived from kernel/capability.c:sys_capget. */
206 rcu_read_lock();
207 cred = __task_cred(target);
208 *effective = cred->cap_effective;
209 *inheritable = cred->cap_inheritable;
210 *permitted = cred->cap_permitted;
211 rcu_read_unlock();
212 return 0;
213 }
214
215 /*
216 * Determine whether the inheritable capabilities are limited to the old
217 * permitted set. Returns 1 if they are limited, 0 if they are not.
218 */
cap_inh_is_capped(void)219 static inline int cap_inh_is_capped(void)
220 {
221 /* they are so limited unless the current task has the CAP_SETPCAP
222 * capability
223 */
224 if (cap_capable(current_cred(), current_cred()->user_ns,
225 CAP_SETPCAP, CAP_OPT_NONE) == 0)
226 return 0;
227 return 1;
228 }
229
230 /**
231 * cap_capset - Validate and apply proposed changes to current's capabilities
232 * @new: The proposed new credentials; alterations should be made here
233 * @old: The current task's current credentials
234 * @effective: A pointer to the proposed new effective capabilities set
235 * @inheritable: A pointer to the proposed new inheritable capabilities set
236 * @permitted: A pointer to the proposed new permitted capabilities set
237 *
238 * This function validates and applies a proposed mass change to the current
239 * process's capability sets. The changes are made to the proposed new
240 * credentials, and assuming no error, will be committed by the caller of LSM.
241 */
cap_capset(struct cred * new,const struct cred * old,const kernel_cap_t * effective,const kernel_cap_t * inheritable,const kernel_cap_t * permitted)242 int cap_capset(struct cred *new,
243 const struct cred *old,
244 const kernel_cap_t *effective,
245 const kernel_cap_t *inheritable,
246 const kernel_cap_t *permitted)
247 {
248 if (cap_inh_is_capped() &&
249 !cap_issubset(*inheritable,
250 cap_combine(old->cap_inheritable,
251 old->cap_permitted)))
252 /* incapable of using this inheritable set */
253 return -EPERM;
254
255 if (!cap_issubset(*inheritable,
256 cap_combine(old->cap_inheritable,
257 old->cap_bset)))
258 /* no new pI capabilities outside bounding set */
259 return -EPERM;
260
261 /* verify restrictions on target's new Permitted set */
262 if (!cap_issubset(*permitted, old->cap_permitted))
263 return -EPERM;
264
265 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
266 if (!cap_issubset(*effective, *permitted))
267 return -EPERM;
268
269 new->cap_effective = *effective;
270 new->cap_inheritable = *inheritable;
271 new->cap_permitted = *permitted;
272
273 /*
274 * Mask off ambient bits that are no longer both permitted and
275 * inheritable.
276 */
277 new->cap_ambient = cap_intersect(new->cap_ambient,
278 cap_intersect(*permitted,
279 *inheritable));
280 if (WARN_ON(!cap_ambient_invariant_ok(new)))
281 return -EINVAL;
282 return 0;
283 }
284
285 /**
286 * cap_inode_need_killpriv - Determine if inode change affects privileges
287 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
288 *
289 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
290 * affects the security markings on that inode, and if it is, should
291 * inode_killpriv() be invoked or the change rejected.
292 *
293 * Return: 1 if security.capability has a value, meaning inode_killpriv()
294 * is required, 0 otherwise, meaning inode_killpriv() is not required.
295 */
cap_inode_need_killpriv(struct dentry * dentry)296 int cap_inode_need_killpriv(struct dentry *dentry)
297 {
298 struct inode *inode = d_backing_inode(dentry);
299 int error;
300
301 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
302 return error > 0;
303 }
304
305 /**
306 * cap_inode_killpriv - Erase the security markings on an inode
307 *
308 * @idmap: idmap of the mount the inode was found from
309 * @dentry: The inode/dentry to alter
310 *
311 * Erase the privilege-enhancing security markings on an inode.
312 *
313 * If the inode has been found through an idmapped mount the idmap of
314 * the vfsmount must be passed through @idmap. This function will then
315 * take care to map the inode according to @idmap before checking
316 * permissions. On non-idmapped mounts or if permission checking is to be
317 * performed on the raw inode simply pass @nop_mnt_idmap.
318 *
319 * Return: 0 if successful, -ve on error.
320 */
cap_inode_killpriv(struct mnt_idmap * idmap,struct dentry * dentry)321 int cap_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry)
322 {
323 int error;
324
325 error = __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS);
326 if (error == -EOPNOTSUPP)
327 error = 0;
328 return error;
329 }
330
rootid_owns_currentns(vfsuid_t rootvfsuid)331 static bool rootid_owns_currentns(vfsuid_t rootvfsuid)
332 {
333 struct user_namespace *ns;
334 kuid_t kroot;
335
336 if (!vfsuid_valid(rootvfsuid))
337 return false;
338
339 kroot = vfsuid_into_kuid(rootvfsuid);
340 for (ns = current_user_ns();; ns = ns->parent) {
341 if (from_kuid(ns, kroot) == 0)
342 return true;
343 if (ns == &init_user_ns)
344 break;
345 }
346
347 return false;
348 }
349
sansflags(__u32 m)350 static __u32 sansflags(__u32 m)
351 {
352 return m & ~VFS_CAP_FLAGS_EFFECTIVE;
353 }
354
is_v2header(int size,const struct vfs_cap_data * cap)355 static bool is_v2header(int size, const struct vfs_cap_data *cap)
356 {
357 if (size != XATTR_CAPS_SZ_2)
358 return false;
359 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
360 }
361
is_v3header(int size,const struct vfs_cap_data * cap)362 static bool is_v3header(int size, const struct vfs_cap_data *cap)
363 {
364 if (size != XATTR_CAPS_SZ_3)
365 return false;
366 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
367 }
368
369 /*
370 * getsecurity: We are called for security.* before any attempt to read the
371 * xattr from the inode itself.
372 *
373 * This gives us a chance to read the on-disk value and convert it. If we
374 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
375 *
376 * Note we are not called by vfs_getxattr_alloc(), but that is only called
377 * by the integrity subsystem, which really wants the unconverted values -
378 * so that's good.
379 */
cap_inode_getsecurity(struct mnt_idmap * idmap,struct inode * inode,const char * name,void ** buffer,bool alloc)380 int cap_inode_getsecurity(struct mnt_idmap *idmap,
381 struct inode *inode, const char *name, void **buffer,
382 bool alloc)
383 {
384 int size;
385 kuid_t kroot;
386 vfsuid_t vfsroot;
387 u32 nsmagic, magic;
388 uid_t root, mappedroot;
389 char *tmpbuf = NULL;
390 struct vfs_cap_data *cap;
391 struct vfs_ns_cap_data *nscap = NULL;
392 struct dentry *dentry;
393 struct user_namespace *fs_ns;
394
395 if (strcmp(name, "capability") != 0)
396 return -EOPNOTSUPP;
397
398 dentry = d_find_any_alias(inode);
399 if (!dentry)
400 return -EINVAL;
401 size = vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, &tmpbuf,
402 sizeof(struct vfs_ns_cap_data), GFP_NOFS);
403 dput(dentry);
404 /* gcc11 complains if we don't check for !tmpbuf */
405 if (size < 0 || !tmpbuf)
406 goto out_free;
407
408 fs_ns = inode->i_sb->s_user_ns;
409 cap = (struct vfs_cap_data *) tmpbuf;
410 if (is_v2header(size, cap)) {
411 root = 0;
412 } else if (is_v3header(size, cap)) {
413 nscap = (struct vfs_ns_cap_data *) tmpbuf;
414 root = le32_to_cpu(nscap->rootid);
415 } else {
416 size = -EINVAL;
417 goto out_free;
418 }
419
420 kroot = make_kuid(fs_ns, root);
421
422 /* If this is an idmapped mount shift the kuid. */
423 vfsroot = make_vfsuid(idmap, fs_ns, kroot);
424
425 /* If the root kuid maps to a valid uid in current ns, then return
426 * this as a nscap. */
427 mappedroot = from_kuid(current_user_ns(), vfsuid_into_kuid(vfsroot));
428 if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
429 size = sizeof(struct vfs_ns_cap_data);
430 if (alloc) {
431 if (!nscap) {
432 /* v2 -> v3 conversion */
433 nscap = kzalloc(size, GFP_ATOMIC);
434 if (!nscap) {
435 size = -ENOMEM;
436 goto out_free;
437 }
438 nsmagic = VFS_CAP_REVISION_3;
439 magic = le32_to_cpu(cap->magic_etc);
440 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
441 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
442 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
443 nscap->magic_etc = cpu_to_le32(nsmagic);
444 } else {
445 /* use allocated v3 buffer */
446 tmpbuf = NULL;
447 }
448 nscap->rootid = cpu_to_le32(mappedroot);
449 *buffer = nscap;
450 }
451 goto out_free;
452 }
453
454 if (!rootid_owns_currentns(vfsroot)) {
455 size = -EOVERFLOW;
456 goto out_free;
457 }
458
459 /* This comes from a parent namespace. Return as a v2 capability */
460 size = sizeof(struct vfs_cap_data);
461 if (alloc) {
462 if (nscap) {
463 /* v3 -> v2 conversion */
464 cap = kzalloc(size, GFP_ATOMIC);
465 if (!cap) {
466 size = -ENOMEM;
467 goto out_free;
468 }
469 magic = VFS_CAP_REVISION_2;
470 nsmagic = le32_to_cpu(nscap->magic_etc);
471 if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
472 magic |= VFS_CAP_FLAGS_EFFECTIVE;
473 memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
474 cap->magic_etc = cpu_to_le32(magic);
475 } else {
476 /* use unconverted v2 */
477 tmpbuf = NULL;
478 }
479 *buffer = cap;
480 }
481 out_free:
482 kfree(tmpbuf);
483 return size;
484 }
485
486 /**
487 * rootid_from_xattr - translate root uid of vfs caps
488 *
489 * @value: vfs caps value which may be modified by this function
490 * @size: size of @ivalue
491 * @task_ns: user namespace of the caller
492 */
rootid_from_xattr(const void * value,size_t size,struct user_namespace * task_ns)493 static vfsuid_t rootid_from_xattr(const void *value, size_t size,
494 struct user_namespace *task_ns)
495 {
496 const struct vfs_ns_cap_data *nscap = value;
497 uid_t rootid = 0;
498
499 if (size == XATTR_CAPS_SZ_3)
500 rootid = le32_to_cpu(nscap->rootid);
501
502 return VFSUIDT_INIT(make_kuid(task_ns, rootid));
503 }
504
validheader(size_t size,const struct vfs_cap_data * cap)505 static bool validheader(size_t size, const struct vfs_cap_data *cap)
506 {
507 return is_v2header(size, cap) || is_v3header(size, cap);
508 }
509
510 /**
511 * cap_convert_nscap - check vfs caps
512 *
513 * @idmap: idmap of the mount the inode was found from
514 * @dentry: used to retrieve inode to check permissions on
515 * @ivalue: vfs caps value which may be modified by this function
516 * @size: size of @ivalue
517 *
518 * User requested a write of security.capability. If needed, update the
519 * xattr to change from v2 to v3, or to fixup the v3 rootid.
520 *
521 * If the inode has been found through an idmapped mount the idmap of
522 * the vfsmount must be passed through @idmap. This function will then
523 * take care to map the inode according to @idmap before checking
524 * permissions. On non-idmapped mounts or if permission checking is to be
525 * performed on the raw inode simply pass @nop_mnt_idmap.
526 *
527 * Return: On success, return the new size; on error, return < 0.
528 */
cap_convert_nscap(struct mnt_idmap * idmap,struct dentry * dentry,const void ** ivalue,size_t size)529 int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry,
530 const void **ivalue, size_t size)
531 {
532 struct vfs_ns_cap_data *nscap;
533 uid_t nsrootid;
534 const struct vfs_cap_data *cap = *ivalue;
535 __u32 magic, nsmagic;
536 struct inode *inode = d_backing_inode(dentry);
537 struct user_namespace *task_ns = current_user_ns(),
538 *fs_ns = inode->i_sb->s_user_ns;
539 kuid_t rootid;
540 vfsuid_t vfsrootid;
541 size_t newsize;
542
543 if (!*ivalue)
544 return -EINVAL;
545 if (!validheader(size, cap))
546 return -EINVAL;
547 if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP))
548 return -EPERM;
549 if (size == XATTR_CAPS_SZ_2 && (idmap == &nop_mnt_idmap))
550 if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
551 /* user is privileged, just write the v2 */
552 return size;
553
554 vfsrootid = rootid_from_xattr(*ivalue, size, task_ns);
555 if (!vfsuid_valid(vfsrootid))
556 return -EINVAL;
557
558 rootid = from_vfsuid(idmap, fs_ns, vfsrootid);
559 if (!uid_valid(rootid))
560 return -EINVAL;
561
562 nsrootid = from_kuid(fs_ns, rootid);
563 if (nsrootid == -1)
564 return -EINVAL;
565
566 newsize = sizeof(struct vfs_ns_cap_data);
567 nscap = kmalloc(newsize, GFP_ATOMIC);
568 if (!nscap)
569 return -ENOMEM;
570 nscap->rootid = cpu_to_le32(nsrootid);
571 nsmagic = VFS_CAP_REVISION_3;
572 magic = le32_to_cpu(cap->magic_etc);
573 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
574 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
575 nscap->magic_etc = cpu_to_le32(nsmagic);
576 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
577
578 *ivalue = nscap;
579 return newsize;
580 }
581
582 /*
583 * Calculate the new process capability sets from the capability sets attached
584 * to a file.
585 */
bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data * caps,struct linux_binprm * bprm,bool * effective,bool * has_fcap)586 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
587 struct linux_binprm *bprm,
588 bool *effective,
589 bool *has_fcap)
590 {
591 struct cred *new = bprm->cred;
592 int ret = 0;
593
594 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
595 *effective = true;
596
597 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
598 *has_fcap = true;
599
600 /*
601 * pP' = (X & fP) | (pI & fI)
602 * The addition of pA' is handled later.
603 */
604 new->cap_permitted.val =
605 (new->cap_bset.val & caps->permitted.val) |
606 (new->cap_inheritable.val & caps->inheritable.val);
607
608 if (caps->permitted.val & ~new->cap_permitted.val)
609 /* insufficient to execute correctly */
610 ret = -EPERM;
611
612 /*
613 * For legacy apps, with no internal support for recognizing they
614 * do not have enough capabilities, we return an error if they are
615 * missing some "forced" (aka file-permitted) capabilities.
616 */
617 return *effective ? ret : 0;
618 }
619
620 /**
621 * get_vfs_caps_from_disk - retrieve vfs caps from disk
622 *
623 * @idmap: idmap of the mount the inode was found from
624 * @dentry: dentry from which @inode is retrieved
625 * @cpu_caps: vfs capabilities
626 *
627 * Extract the on-exec-apply capability sets for an executable file.
628 *
629 * If the inode has been found through an idmapped mount the idmap of
630 * the vfsmount must be passed through @idmap. This function will then
631 * take care to map the inode according to @idmap before checking
632 * permissions. On non-idmapped mounts or if permission checking is to be
633 * performed on the raw inode simply pass @nop_mnt_idmap.
634 */
get_vfs_caps_from_disk(struct mnt_idmap * idmap,const struct dentry * dentry,struct cpu_vfs_cap_data * cpu_caps)635 int get_vfs_caps_from_disk(struct mnt_idmap *idmap,
636 const struct dentry *dentry,
637 struct cpu_vfs_cap_data *cpu_caps)
638 {
639 struct inode *inode = d_backing_inode(dentry);
640 __u32 magic_etc;
641 int size;
642 struct vfs_ns_cap_data data, *nscaps = &data;
643 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
644 kuid_t rootkuid;
645 vfsuid_t rootvfsuid;
646 struct user_namespace *fs_ns;
647
648 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
649
650 if (!inode)
651 return -ENODATA;
652
653 fs_ns = inode->i_sb->s_user_ns;
654 size = __vfs_getxattr((struct dentry *)dentry, inode,
655 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
656 if (size == -ENODATA || size == -EOPNOTSUPP)
657 /* no data, that's ok */
658 return -ENODATA;
659
660 if (size < 0)
661 return size;
662
663 if (size < sizeof(magic_etc))
664 return -EINVAL;
665
666 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
667
668 rootkuid = make_kuid(fs_ns, 0);
669 switch (magic_etc & VFS_CAP_REVISION_MASK) {
670 case VFS_CAP_REVISION_1:
671 if (size != XATTR_CAPS_SZ_1)
672 return -EINVAL;
673 break;
674 case VFS_CAP_REVISION_2:
675 if (size != XATTR_CAPS_SZ_2)
676 return -EINVAL;
677 break;
678 case VFS_CAP_REVISION_3:
679 if (size != XATTR_CAPS_SZ_3)
680 return -EINVAL;
681 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
682 break;
683
684 default:
685 return -EINVAL;
686 }
687
688 rootvfsuid = make_vfsuid(idmap, fs_ns, rootkuid);
689 if (!vfsuid_valid(rootvfsuid))
690 return -ENODATA;
691
692 /* Limit the caps to the mounter of the filesystem
693 * or the more limited uid specified in the xattr.
694 */
695 if (!rootid_owns_currentns(rootvfsuid))
696 return -ENODATA;
697
698 cpu_caps->permitted.val = le32_to_cpu(caps->data[0].permitted);
699 cpu_caps->inheritable.val = le32_to_cpu(caps->data[0].inheritable);
700
701 /*
702 * Rev1 had just a single 32-bit word, later expanded
703 * to a second one for the high bits
704 */
705 if ((magic_etc & VFS_CAP_REVISION_MASK) != VFS_CAP_REVISION_1) {
706 cpu_caps->permitted.val += (u64)le32_to_cpu(caps->data[1].permitted) << 32;
707 cpu_caps->inheritable.val += (u64)le32_to_cpu(caps->data[1].inheritable) << 32;
708 }
709
710 cpu_caps->permitted.val &= CAP_VALID_MASK;
711 cpu_caps->inheritable.val &= CAP_VALID_MASK;
712
713 cpu_caps->rootid = vfsuid_into_kuid(rootvfsuid);
714
715 return 0;
716 }
717
718 /*
719 * Attempt to get the on-exec apply capability sets for an executable file from
720 * its xattrs and, if present, apply them to the proposed credentials being
721 * constructed by execve().
722 */
get_file_caps(struct linux_binprm * bprm,struct file * file,bool * effective,bool * has_fcap)723 static int get_file_caps(struct linux_binprm *bprm, struct file *file,
724 bool *effective, bool *has_fcap)
725 {
726 int rc = 0;
727 struct cpu_vfs_cap_data vcaps;
728
729 cap_clear(bprm->cred->cap_permitted);
730
731 if (!file_caps_enabled)
732 return 0;
733
734 if (!mnt_may_suid(file->f_path.mnt))
735 return 0;
736
737 /*
738 * This check is redundant with mnt_may_suid() but is kept to make
739 * explicit that capability bits are limited to s_user_ns and its
740 * descendants.
741 */
742 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
743 return 0;
744
745 rc = get_vfs_caps_from_disk(file_mnt_idmap(file),
746 file->f_path.dentry, &vcaps);
747 if (rc < 0) {
748 if (rc == -EINVAL)
749 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
750 bprm->filename);
751 else if (rc == -ENODATA)
752 rc = 0;
753 goto out;
754 }
755
756 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
757
758 out:
759 if (rc)
760 cap_clear(bprm->cred->cap_permitted);
761
762 return rc;
763 }
764
root_privileged(void)765 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
766
__is_real(kuid_t uid,struct cred * cred)767 static inline bool __is_real(kuid_t uid, struct cred *cred)
768 { return uid_eq(cred->uid, uid); }
769
__is_eff(kuid_t uid,struct cred * cred)770 static inline bool __is_eff(kuid_t uid, struct cred *cred)
771 { return uid_eq(cred->euid, uid); }
772
__is_suid(kuid_t uid,struct cred * cred)773 static inline bool __is_suid(kuid_t uid, struct cred *cred)
774 { return !__is_real(uid, cred) && __is_eff(uid, cred); }
775
776 /*
777 * handle_privileged_root - Handle case of privileged root
778 * @bprm: The execution parameters, including the proposed creds
779 * @has_fcap: Are any file capabilities set?
780 * @effective: Do we have effective root privilege?
781 * @root_uid: This namespace' root UID WRT initial USER namespace
782 *
783 * Handle the case where root is privileged and hasn't been neutered by
784 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
785 * set UID root and nothing is changed. If we are root, cap_permitted is
786 * updated. If we have become set UID root, the effective bit is set.
787 */
handle_privileged_root(struct linux_binprm * bprm,bool has_fcap,bool * effective,kuid_t root_uid)788 static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
789 bool *effective, kuid_t root_uid)
790 {
791 const struct cred *old = current_cred();
792 struct cred *new = bprm->cred;
793
794 if (!root_privileged())
795 return;
796 /*
797 * If the legacy file capability is set, then don't set privs
798 * for a setuid root binary run by a non-root user. Do set it
799 * for a root user just to cause least surprise to an admin.
800 */
801 if (has_fcap && __is_suid(root_uid, new)) {
802 warn_setuid_and_fcaps_mixed(bprm->filename);
803 return;
804 }
805 /*
806 * To support inheritance of root-permissions and suid-root
807 * executables under compatibility mode, we override the
808 * capability sets for the file.
809 */
810 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
811 /* pP' = (cap_bset & ~0) | (pI & ~0) */
812 new->cap_permitted = cap_combine(old->cap_bset,
813 old->cap_inheritable);
814 }
815 /*
816 * If only the real uid is 0, we do not set the effective bit.
817 */
818 if (__is_eff(root_uid, new))
819 *effective = true;
820 }
821
822 #define __cap_gained(field, target, source) \
823 !cap_issubset(target->cap_##field, source->cap_##field)
824 #define __cap_grew(target, source, cred) \
825 !cap_issubset(cred->cap_##target, cred->cap_##source)
826 #define __cap_full(field, cred) \
827 cap_issubset(CAP_FULL_SET, cred->cap_##field)
828
__is_setuid(struct cred * new,const struct cred * old)829 static inline bool __is_setuid(struct cred *new, const struct cred *old)
830 { return !uid_eq(new->euid, old->uid); }
831
__is_setgid(struct cred * new,const struct cred * old)832 static inline bool __is_setgid(struct cred *new, const struct cred *old)
833 { return !gid_eq(new->egid, old->gid); }
834
835 /*
836 * 1) Audit candidate if current->cap_effective is set
837 *
838 * We do not bother to audit if 3 things are true:
839 * 1) cap_effective has all caps
840 * 2) we became root *OR* are were already root
841 * 3) root is supposed to have all caps (SECURE_NOROOT)
842 * Since this is just a normal root execing a process.
843 *
844 * Number 1 above might fail if you don't have a full bset, but I think
845 * that is interesting information to audit.
846 *
847 * A number of other conditions require logging:
848 * 2) something prevented setuid root getting all caps
849 * 3) non-setuid root gets fcaps
850 * 4) non-setuid root gets ambient
851 */
nonroot_raised_pE(struct cred * new,const struct cred * old,kuid_t root,bool has_fcap)852 static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
853 kuid_t root, bool has_fcap)
854 {
855 bool ret = false;
856
857 if ((__cap_grew(effective, ambient, new) &&
858 !(__cap_full(effective, new) &&
859 (__is_eff(root, new) || __is_real(root, new)) &&
860 root_privileged())) ||
861 (root_privileged() &&
862 __is_suid(root, new) &&
863 !__cap_full(effective, new)) ||
864 (!__is_setuid(new, old) &&
865 ((has_fcap &&
866 __cap_gained(permitted, new, old)) ||
867 __cap_gained(ambient, new, old))))
868
869 ret = true;
870
871 return ret;
872 }
873
874 /**
875 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
876 * @bprm: The execution parameters, including the proposed creds
877 * @file: The file to pull the credentials from
878 *
879 * Set up the proposed credentials for a new execution context being
880 * constructed by execve(). The proposed creds in @bprm->cred is altered,
881 * which won't take effect immediately.
882 *
883 * Return: 0 if successful, -ve on error.
884 */
cap_bprm_creds_from_file(struct linux_binprm * bprm,struct file * file)885 int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
886 {
887 /* Process setpcap binaries and capabilities for uid 0 */
888 const struct cred *old = current_cred();
889 struct cred *new = bprm->cred;
890 bool effective = false, has_fcap = false, is_setid;
891 int ret;
892 kuid_t root_uid;
893
894 if (WARN_ON(!cap_ambient_invariant_ok(old)))
895 return -EPERM;
896
897 ret = get_file_caps(bprm, file, &effective, &has_fcap);
898 if (ret < 0)
899 return ret;
900
901 root_uid = make_kuid(new->user_ns, 0);
902
903 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
904
905 /* if we have fs caps, clear dangerous personality flags */
906 if (__cap_gained(permitted, new, old))
907 bprm->per_clear |= PER_CLEAR_ON_SETID;
908
909 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
910 * credentials unless they have the appropriate permit.
911 *
912 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
913 */
914 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
915
916 if ((is_setid || __cap_gained(permitted, new, old)) &&
917 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
918 !ptracer_capable(current, new->user_ns))) {
919 /* downgrade; they get no more than they had, and maybe less */
920 if (!ns_capable(new->user_ns, CAP_SETUID) ||
921 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
922 new->euid = new->uid;
923 new->egid = new->gid;
924 }
925 new->cap_permitted = cap_intersect(new->cap_permitted,
926 old->cap_permitted);
927 }
928
929 new->suid = new->fsuid = new->euid;
930 new->sgid = new->fsgid = new->egid;
931
932 /* File caps or setid cancels ambient. */
933 if (has_fcap || is_setid)
934 cap_clear(new->cap_ambient);
935
936 /*
937 * Now that we've computed pA', update pP' to give:
938 * pP' = (X & fP) | (pI & fI) | pA'
939 */
940 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
941
942 /*
943 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
944 * this is the same as pE' = (fE ? pP' : 0) | pA'.
945 */
946 if (effective)
947 new->cap_effective = new->cap_permitted;
948 else
949 new->cap_effective = new->cap_ambient;
950
951 if (WARN_ON(!cap_ambient_invariant_ok(new)))
952 return -EPERM;
953
954 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
955 ret = audit_log_bprm_fcaps(bprm, new, old);
956 if (ret < 0)
957 return ret;
958 }
959
960 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
961
962 if (WARN_ON(!cap_ambient_invariant_ok(new)))
963 return -EPERM;
964
965 /* Check for privilege-elevated exec. */
966 if (is_setid ||
967 (!__is_real(root_uid, new) &&
968 (effective ||
969 __cap_grew(permitted, ambient, new))))
970 bprm->secureexec = 1;
971
972 return 0;
973 }
974
975 /**
976 * cap_inode_setxattr - Determine whether an xattr may be altered
977 * @dentry: The inode/dentry being altered
978 * @name: The name of the xattr to be changed
979 * @value: The value that the xattr will be changed to
980 * @size: The size of value
981 * @flags: The replacement flag
982 *
983 * Determine whether an xattr may be altered or set on an inode, returning 0 if
984 * permission is granted, -ve if denied.
985 *
986 * This is used to make sure security xattrs don't get updated or set by those
987 * who aren't privileged to do so.
988 */
cap_inode_setxattr(struct dentry * dentry,const char * name,const void * value,size_t size,int flags)989 int cap_inode_setxattr(struct dentry *dentry, const char *name,
990 const void *value, size_t size, int flags)
991 {
992 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
993
994 /* Ignore non-security xattrs */
995 if (strncmp(name, XATTR_SECURITY_PREFIX,
996 XATTR_SECURITY_PREFIX_LEN) != 0)
997 return 0;
998
999 /*
1000 * For XATTR_NAME_CAPS the check will be done in
1001 * cap_convert_nscap(), called by setxattr()
1002 */
1003 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1004 return 0;
1005
1006 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1007 return -EPERM;
1008 return 0;
1009 }
1010
1011 /**
1012 * cap_inode_removexattr - Determine whether an xattr may be removed
1013 *
1014 * @idmap: idmap of the mount the inode was found from
1015 * @dentry: The inode/dentry being altered
1016 * @name: The name of the xattr to be changed
1017 *
1018 * Determine whether an xattr may be removed from an inode, returning 0 if
1019 * permission is granted, -ve if denied.
1020 *
1021 * If the inode has been found through an idmapped mount the idmap of
1022 * the vfsmount must be passed through @idmap. This function will then
1023 * take care to map the inode according to @idmap before checking
1024 * permissions. On non-idmapped mounts or if permission checking is to be
1025 * performed on the raw inode simply pass @nop_mnt_idmap.
1026 *
1027 * This is used to make sure security xattrs don't get removed by those who
1028 * aren't privileged to remove them.
1029 */
cap_inode_removexattr(struct mnt_idmap * idmap,struct dentry * dentry,const char * name)1030 int cap_inode_removexattr(struct mnt_idmap *idmap,
1031 struct dentry *dentry, const char *name)
1032 {
1033 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1034
1035 /* Ignore non-security xattrs */
1036 if (strncmp(name, XATTR_SECURITY_PREFIX,
1037 XATTR_SECURITY_PREFIX_LEN) != 0)
1038 return 0;
1039
1040 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1041 /* security.capability gets namespaced */
1042 struct inode *inode = d_backing_inode(dentry);
1043 if (!inode)
1044 return -EINVAL;
1045 if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP))
1046 return -EPERM;
1047 return 0;
1048 }
1049
1050 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1051 return -EPERM;
1052 return 0;
1053 }
1054
1055 /*
1056 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1057 * a process after a call to setuid, setreuid, or setresuid.
1058 *
1059 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1060 * {r,e,s}uid != 0, the permitted and effective capabilities are
1061 * cleared.
1062 *
1063 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1064 * capabilities of the process are cleared.
1065 *
1066 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1067 * capabilities are set to the permitted capabilities.
1068 *
1069 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1070 * never happen.
1071 *
1072 * -astor
1073 *
1074 * cevans - New behaviour, Oct '99
1075 * A process may, via prctl(), elect to keep its capabilities when it
1076 * calls setuid() and switches away from uid==0. Both permitted and
1077 * effective sets will be retained.
1078 * Without this change, it was impossible for a daemon to drop only some
1079 * of its privilege. The call to setuid(!=0) would drop all privileges!
1080 * Keeping uid 0 is not an option because uid 0 owns too many vital
1081 * files..
1082 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1083 */
cap_emulate_setxuid(struct cred * new,const struct cred * old)1084 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1085 {
1086 kuid_t root_uid = make_kuid(old->user_ns, 0);
1087
1088 if ((uid_eq(old->uid, root_uid) ||
1089 uid_eq(old->euid, root_uid) ||
1090 uid_eq(old->suid, root_uid)) &&
1091 (!uid_eq(new->uid, root_uid) &&
1092 !uid_eq(new->euid, root_uid) &&
1093 !uid_eq(new->suid, root_uid))) {
1094 if (!issecure(SECURE_KEEP_CAPS)) {
1095 cap_clear(new->cap_permitted);
1096 cap_clear(new->cap_effective);
1097 }
1098
1099 /*
1100 * Pre-ambient programs expect setresuid to nonroot followed
1101 * by exec to drop capabilities. We should make sure that
1102 * this remains the case.
1103 */
1104 cap_clear(new->cap_ambient);
1105 }
1106 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1107 cap_clear(new->cap_effective);
1108 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1109 new->cap_effective = new->cap_permitted;
1110 }
1111
1112 /**
1113 * cap_task_fix_setuid - Fix up the results of setuid() call
1114 * @new: The proposed credentials
1115 * @old: The current task's current credentials
1116 * @flags: Indications of what has changed
1117 *
1118 * Fix up the results of setuid() call before the credential changes are
1119 * actually applied.
1120 *
1121 * Return: 0 to grant the changes, -ve to deny them.
1122 */
cap_task_fix_setuid(struct cred * new,const struct cred * old,int flags)1123 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1124 {
1125 switch (flags) {
1126 case LSM_SETID_RE:
1127 case LSM_SETID_ID:
1128 case LSM_SETID_RES:
1129 /* juggle the capabilities to follow [RES]UID changes unless
1130 * otherwise suppressed */
1131 if (!issecure(SECURE_NO_SETUID_FIXUP))
1132 cap_emulate_setxuid(new, old);
1133 break;
1134
1135 case LSM_SETID_FS:
1136 /* juggle the capabilities to follow FSUID changes, unless
1137 * otherwise suppressed
1138 *
1139 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1140 * if not, we might be a bit too harsh here.
1141 */
1142 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1143 kuid_t root_uid = make_kuid(old->user_ns, 0);
1144 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1145 new->cap_effective =
1146 cap_drop_fs_set(new->cap_effective);
1147
1148 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1149 new->cap_effective =
1150 cap_raise_fs_set(new->cap_effective,
1151 new->cap_permitted);
1152 }
1153 break;
1154
1155 default:
1156 return -EINVAL;
1157 }
1158
1159 return 0;
1160 }
1161
1162 /*
1163 * Rationale: code calling task_setscheduler, task_setioprio, and
1164 * task_setnice, assumes that
1165 * . if capable(cap_sys_nice), then those actions should be allowed
1166 * . if not capable(cap_sys_nice), but acting on your own processes,
1167 * then those actions should be allowed
1168 * This is insufficient now since you can call code without suid, but
1169 * yet with increased caps.
1170 * So we check for increased caps on the target process.
1171 */
cap_safe_nice(struct task_struct * p)1172 static int cap_safe_nice(struct task_struct *p)
1173 {
1174 int is_subset, ret = 0;
1175
1176 rcu_read_lock();
1177 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1178 current_cred()->cap_permitted);
1179 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1180 ret = -EPERM;
1181 rcu_read_unlock();
1182
1183 return ret;
1184 }
1185
1186 /**
1187 * cap_task_setscheduler - Determine if scheduler policy change is permitted
1188 * @p: The task to affect
1189 *
1190 * Determine if the requested scheduler policy change is permitted for the
1191 * specified task.
1192 *
1193 * Return: 0 if permission is granted, -ve if denied.
1194 */
cap_task_setscheduler(struct task_struct * p)1195 int cap_task_setscheduler(struct task_struct *p)
1196 {
1197 return cap_safe_nice(p);
1198 }
1199
1200 /**
1201 * cap_task_setioprio - Determine if I/O priority change is permitted
1202 * @p: The task to affect
1203 * @ioprio: The I/O priority to set
1204 *
1205 * Determine if the requested I/O priority change is permitted for the specified
1206 * task.
1207 *
1208 * Return: 0 if permission is granted, -ve if denied.
1209 */
cap_task_setioprio(struct task_struct * p,int ioprio)1210 int cap_task_setioprio(struct task_struct *p, int ioprio)
1211 {
1212 return cap_safe_nice(p);
1213 }
1214
1215 /**
1216 * cap_task_setnice - Determine if task priority change is permitted
1217 * @p: The task to affect
1218 * @nice: The nice value to set
1219 *
1220 * Determine if the requested task priority change is permitted for the
1221 * specified task.
1222 *
1223 * Return: 0 if permission is granted, -ve if denied.
1224 */
cap_task_setnice(struct task_struct * p,int nice)1225 int cap_task_setnice(struct task_struct *p, int nice)
1226 {
1227 return cap_safe_nice(p);
1228 }
1229
1230 /*
1231 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1232 * the current task's bounding set. Returns 0 on success, -ve on error.
1233 */
cap_prctl_drop(unsigned long cap)1234 static int cap_prctl_drop(unsigned long cap)
1235 {
1236 struct cred *new;
1237
1238 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1239 return -EPERM;
1240 if (!cap_valid(cap))
1241 return -EINVAL;
1242
1243 new = prepare_creds();
1244 if (!new)
1245 return -ENOMEM;
1246 cap_lower(new->cap_bset, cap);
1247 return commit_creds(new);
1248 }
1249
1250 /**
1251 * cap_task_prctl - Implement process control functions for this security module
1252 * @option: The process control function requested
1253 * @arg2: The argument data for this function
1254 * @arg3: The argument data for this function
1255 * @arg4: The argument data for this function
1256 * @arg5: The argument data for this function
1257 *
1258 * Allow process control functions (sys_prctl()) to alter capabilities; may
1259 * also deny access to other functions not otherwise implemented here.
1260 *
1261 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1262 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1263 * modules will consider performing the function.
1264 */
cap_task_prctl(int option,unsigned long arg2,unsigned long arg3,unsigned long arg4,unsigned long arg5)1265 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1266 unsigned long arg4, unsigned long arg5)
1267 {
1268 const struct cred *old = current_cred();
1269 struct cred *new;
1270
1271 switch (option) {
1272 case PR_CAPBSET_READ:
1273 if (!cap_valid(arg2))
1274 return -EINVAL;
1275 return !!cap_raised(old->cap_bset, arg2);
1276
1277 case PR_CAPBSET_DROP:
1278 return cap_prctl_drop(arg2);
1279
1280 /*
1281 * The next four prctl's remain to assist with transitioning a
1282 * system from legacy UID=0 based privilege (when filesystem
1283 * capabilities are not in use) to a system using filesystem
1284 * capabilities only - as the POSIX.1e draft intended.
1285 *
1286 * Note:
1287 *
1288 * PR_SET_SECUREBITS =
1289 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1290 * | issecure_mask(SECURE_NOROOT)
1291 * | issecure_mask(SECURE_NOROOT_LOCKED)
1292 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1293 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1294 *
1295 * will ensure that the current process and all of its
1296 * children will be locked into a pure
1297 * capability-based-privilege environment.
1298 */
1299 case PR_SET_SECUREBITS:
1300 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1301 & (old->securebits ^ arg2)) /*[1]*/
1302 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
1303 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
1304 || (cap_capable(current_cred(),
1305 current_cred()->user_ns,
1306 CAP_SETPCAP,
1307 CAP_OPT_NONE) != 0) /*[4]*/
1308 /*
1309 * [1] no changing of bits that are locked
1310 * [2] no unlocking of locks
1311 * [3] no setting of unsupported bits
1312 * [4] doing anything requires privilege (go read about
1313 * the "sendmail capabilities bug")
1314 */
1315 )
1316 /* cannot change a locked bit */
1317 return -EPERM;
1318
1319 new = prepare_creds();
1320 if (!new)
1321 return -ENOMEM;
1322 new->securebits = arg2;
1323 return commit_creds(new);
1324
1325 case PR_GET_SECUREBITS:
1326 return old->securebits;
1327
1328 case PR_GET_KEEPCAPS:
1329 return !!issecure(SECURE_KEEP_CAPS);
1330
1331 case PR_SET_KEEPCAPS:
1332 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1333 return -EINVAL;
1334 if (issecure(SECURE_KEEP_CAPS_LOCKED))
1335 return -EPERM;
1336
1337 new = prepare_creds();
1338 if (!new)
1339 return -ENOMEM;
1340 if (arg2)
1341 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1342 else
1343 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1344 return commit_creds(new);
1345
1346 case PR_CAP_AMBIENT:
1347 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1348 if (arg3 | arg4 | arg5)
1349 return -EINVAL;
1350
1351 new = prepare_creds();
1352 if (!new)
1353 return -ENOMEM;
1354 cap_clear(new->cap_ambient);
1355 return commit_creds(new);
1356 }
1357
1358 if (((!cap_valid(arg3)) | arg4 | arg5))
1359 return -EINVAL;
1360
1361 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1362 return !!cap_raised(current_cred()->cap_ambient, arg3);
1363 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1364 arg2 != PR_CAP_AMBIENT_LOWER) {
1365 return -EINVAL;
1366 } else {
1367 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1368 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1369 !cap_raised(current_cred()->cap_inheritable,
1370 arg3) ||
1371 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1372 return -EPERM;
1373
1374 new = prepare_creds();
1375 if (!new)
1376 return -ENOMEM;
1377 if (arg2 == PR_CAP_AMBIENT_RAISE)
1378 cap_raise(new->cap_ambient, arg3);
1379 else
1380 cap_lower(new->cap_ambient, arg3);
1381 return commit_creds(new);
1382 }
1383
1384 default:
1385 /* No functionality available - continue with default */
1386 return -ENOSYS;
1387 }
1388 }
1389
1390 /**
1391 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1392 * @mm: The VM space in which the new mapping is to be made
1393 * @pages: The size of the mapping
1394 *
1395 * Determine whether the allocation of a new virtual mapping by the current
1396 * task is permitted.
1397 *
1398 * Return: 1 if permission is granted, 0 if not.
1399 */
cap_vm_enough_memory(struct mm_struct * mm,long pages)1400 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1401 {
1402 int cap_sys_admin = 0;
1403
1404 if (cap_capable(current_cred(), &init_user_ns,
1405 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1406 cap_sys_admin = 1;
1407
1408 return cap_sys_admin;
1409 }
1410
1411 /**
1412 * cap_mmap_addr - check if able to map given addr
1413 * @addr: address attempting to be mapped
1414 *
1415 * If the process is attempting to map memory below dac_mmap_min_addr they need
1416 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1417 * capability security module.
1418 *
1419 * Return: 0 if this mapping should be allowed or -EPERM if not.
1420 */
cap_mmap_addr(unsigned long addr)1421 int cap_mmap_addr(unsigned long addr)
1422 {
1423 int ret = 0;
1424
1425 if (addr < dac_mmap_min_addr) {
1426 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1427 CAP_OPT_NONE);
1428 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1429 if (ret == 0)
1430 current->flags |= PF_SUPERPRIV;
1431 }
1432 return ret;
1433 }
1434
cap_mmap_file(struct file * file,unsigned long reqprot,unsigned long prot,unsigned long flags)1435 int cap_mmap_file(struct file *file, unsigned long reqprot,
1436 unsigned long prot, unsigned long flags)
1437 {
1438 return 0;
1439 }
1440
1441 #ifdef CONFIG_SECURITY
1442
1443 static struct security_hook_list capability_hooks[] __ro_after_init = {
1444 LSM_HOOK_INIT(capable, cap_capable),
1445 LSM_HOOK_INIT(settime, cap_settime),
1446 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1447 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1448 LSM_HOOK_INIT(capget, cap_capget),
1449 LSM_HOOK_INIT(capset, cap_capset),
1450 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1451 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1452 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1453 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1454 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1455 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1456 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1457 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1458 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1459 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1460 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1461 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1462 };
1463
capability_init(void)1464 static int __init capability_init(void)
1465 {
1466 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1467 "capability");
1468 return 0;
1469 }
1470
1471 DEFINE_LSM(capability) = {
1472 .name = "capability",
1473 .order = LSM_ORDER_FIRST,
1474 .init = capability_init,
1475 };
1476
1477 #endif /* CONFIG_SECURITY */
1478
